On 02/01/2020 02:15, Graham c wrote:
I have been working through the code that does the encoding of
standard messages in FT8 with a goal of creating a simplified version
that can compiled and used on an atmega328 processor (i.e. Arduino).
There is an Arduino library called JTEncode which includes FT8 but
this only encodes free text messages limited to 13 characters. So, I
can encode something like CQ N2NCZ FN03 but CQ VE3GHM FN25 get
truncated to 13 characters and drops the 5 from the grid square.
The problem I am having is not being able to work my way through the
code but rather the use of 64bit (8 byte) may in the pack28 call sign
hash routines. The atmega328 is an 8 bit controller and Arduino is
limited to 32 bits (i.e. 4 byte) and I have so far been unable to come
up with some workaround that lets me do this 64 bit stuff on Arduino
without getting very messy and consuming far too much of the very
limited ram available.
Which brings me to my question - is anyone aware of any code for
encoding FT8 standard messages that can use 32bit math on something
like the atmeag328 / Arduino?
cheers, Graham ve3gtc
Hi Graham,
free text messages involve the biggest numbers as they require a 71-bit
field. The maths required should not be that challenging for an 8-bit
CPU core like the AVR since the main operations are bitwise or addition,
addition only requires a basic carry operation to extend the length past
8-bits.
Although encoding FT8 on a small 8-bit MCU is an interesting academic
exercise you should keep in mind that FT8 is a QSO mode so any
implementation that does not include decoding will not be providing
anything particularly useful. Decoding FT8 to any sort of workable time
schedule in not possible on a CPU with only a few MHz clock speed. You
may be thinking of beacon type operations, I would strongly suggest
looking at WSPR, or perhaps JT9 since both have greatly better
sensitivity while using less bandwidth.
73
Bill
G4WJS.
_______________________________________________
wsjt-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/wsjt-devel
